The present invention relates to a radiation collimator for high energy radiation beams, and in particular to a collimator for use in x-ray systems used primarily for diagnosis and treatment of the human body.
In the use of x-ray systems on the human body it is desirable that the beam of radiation, which impinges on the subject, be narrowly confined to the specific area of interest or treatment and prevented from impinging on other areas which might be damaged by undesirable radiation. Such undesirable radiation is emitted from off-focal spots in the x-ray generating tube. It has been found that such off-focus radiation can be best controlled and prevented from passing through subsequent collimator shutter devices by positioning collimator radiation absorbing elements as closely as possible to the x-ray tube generator. This permits greater control over the cross-sectional size and shape of the beam of radiation.
A number of radiation collimator structures have been designed to solve this problem; a few are described in U.S. Pat. Nos. 3,448,270; 3,127,514; 3,609,370; 3,304,427; 3,023,324; and 3,156,824. One problem with these collimator devices is that they are very complicated arrangements of radiation absorbing shutter elements which usually take the form of a pyramidal shape, which is adjustable to effect an increase or decrease in an aperture defined by the narrow end of the pyramid. In addition, the structural support for these radiation absorbing elements being complex introduces problems in controlling and minimizing the erosion of the elements at their surface areas of contact as they operate with one another. Accordingly, such prior art devices have a high manufacturing cost, are difficult to repair and replacement of parts is a time-consuming effort.